fix multi-profile

tests/node_tests/multi_profile.py

@@ -31,3 +31,41 @@ def test_vertical_direction():
     field = make_field(shape=(80, 40))
     (profile,) = node.process(field, field, row=-1, direction="vertical", mode="overlay")
     assert len(profile.data) == 80, f"Vertical profile length should be field height (80), got {len(profile.data)}"
+
+
+def test_emits_blended_overlay():
+    from backend.execution_context import active_node, execution_callbacks
+    from backend.nodes.multi_profile import MultipleProfiles
+
+    node = MultipleProfiles()
+    field = make_field(shape=(64, 128))
+
+    overlays = []
+    with execution_callbacks(overlay=lambda nid, d: overlays.append(d)), active_node("test"):
+        node.process(field, field, row=10, direction="horizontal", mode="overlay")
+
+    assert len(overlays) == 1
+    ov = overlays[0]
+    assert ov["kind"] == "multi_profile"
+    assert ov["section_title"] == "Preview"
+    assert ov["image"].startswith("data:image/png;base64,")
+    assert ov["row"] == 10
+    assert ov["direction"] == "horizontal"
+    assert ov["max_index"] == 63  # height - 1
+
+
+def test_overlay_max_index_for_vertical():
+    from backend.execution_context import active_node, execution_callbacks
+    from backend.nodes.multi_profile import MultipleProfiles
+
+    node = MultipleProfiles()
+    field = make_field(shape=(80, 40))
+
+    overlays = []
+    with execution_callbacks(overlay=lambda nid, d: overlays.append(d)), active_node("test"):
+        node.process(field, field, row=-1, direction="vertical", mode="overlay")
+
+    ov = overlays[0]
+    assert ov["direction"] == "vertical"
+    assert ov["max_index"] == 39  # width - 1
+    assert ov["row"] == 20  # center column for 40 wide